Rigging for mobile tower crane having a topping jib-boom



May 24, 1966 J. E. WIESCHEL 3,252,585

RIGGING FOR MOBILE TOWER CRANE HAVING A I'OPPING JIB-BOOM Filed Dec. 21, 1964 INVENTOR. JOHN E. WIESCHEL Arramve-Y United States Patent 3,252,585 RIGGING FOR MOBILE TOWER CRANE HAVING A TOPPING Jill-BOOM John E. Wieschel, Waulresha, Wis., assignor to Harnischfeger Corporation, Milwaukee, Wis., a corporatlon of Wisconsin Filed Dec. 21, 1964, Ser. No. 419,815 4 Claims. (Cl. 21259) This invention relates to a mobile tower crane of the type adapted for use in building construction. These tower cranes have a high tower which in operation extends upwardly in a vertical position, and a jib-boom pivotally mounted at one end to the upper end of the tower for vertical swinging relative to the tower. These cranes are mounted on a turret to permit rotation thereof about a vertical axis, and the turret is mounted on a mobile unit, such as, a rubber-tired truck.

In prior art devices of the above type, a cable reeving system is first used for erecting or topping the tower to a vertical position; this system properly used does not bend the tower backward about the backstops. A second cable reeving system is employed to erect or top the jib-boom about its pivot at the top of the tower; this prior art system, anchored to some part of the revolving upper frame or turret at a distance from the tower pivot, will impose a moment on the tower tending to bend it backwards about the backstops. This is an undesirable condition which this invention eliminates.

Another problem arises when, if for some reason, the load is suddenly relieved, gives way. is dropped, or otherwise accelerates, there is a sharp jerking or swinging movement of the tower due to the cable system acting through the above-mentioned moment arm. This reaction also tends to pull backward on the tower, throwing an additional and sometimes severe load on the tower backstop, and generally creating an unstable condition and attitude of the boom and the entire crane.

Accordingly, the present invention provides an improved mobile tower crane having a vertically swingable jib-boom mounted on top of a tower, and which eliminates the above-mentioned shortcomings and disadvantages of the prior art. More specifically, the present invention provides a mobile crane of the above type in which the undesirable moment arm between the tower and anchor end of the cable system has been eliminated; instead, the jib-boom topping cable system is anchored directly to the tower adjacent the lower end thereof. As a result, stability of the tower and the entire crane has been greatly increased under all operating conditions.

These and other objects and advantages of the present invention will appear hereinafter as this disclosure progresses, reference being had to the accompanying drawings, in which:

FIGURE 1 is a side elevational view of a mobile tower crane embodying the present invention;

FIGURE 2 is an enlarged, fragmentary view of a portion of the device shown in FIGURE 1; and

FIGURE 3 is a view taken along line 33 in FIGURE 2, but on an enlarged scale, showing the jib boom cable reeving or spreader system and its anchor to the tower.

Referring in greater detail to the drawings, a conventional motorized crane carrier 1 includes a drivers cab 2, chassis 3, heavyduty rubber tires 4, outrigger 5, and turntable 6 on which a crane cab 7 is mounted. The cab 7 includes the hoisting mechanism including the tower hoist drum. 8 and the hoist drum 9 for the jib-boom cable system to be described.

A tower 12 is pivoted at 13 to the crane cab 7 and in operation may extend vertically to any predetermined, considerable height. The tower 12 itself is conventional and has a cap 14 at its upper end to which a jib-boom 15 ice is pivotally attached at the front side of the cap, as at 16. For supporting the tower in substantiallyvertical position, a tower suspension cable 17 is secured at its upper end 18 to the top of the tower and is secured at its lower end to the rigid frame 19 on cab 7 as at 20. The suspension cable includes a cable reeving or spreader assembly 21 having a cable 22 that :is wound on the tower hoist drum 8. The drum 8 is used to hoist the tower into its vertical position where it is held by a pair of rigid backstop memhere 24, 25.

These rigid backstop members are located at the back side of the tower and are mounted at their upper ends on shaft 26 which in turn is securely held in brackets 27, 28 fixed to the tower .12.

Shaft 26 is mounted adjacent the lower end of the tower and can also serve as an anchor for the cable system which vertically positions the jib-boom 15. More specifically, a lower spreader 30 is secured to shaft 26 and has two pairs of sheaves 31 and 32 mounted thereon. The jibboom reeving system also includes an upper spreader 34 having pairs of sheaves 35, 36 thereon. A cable 37 is trained around these multiple sheaves 31, 32, 35, and 36 and then is connected to the drum 9. Hoist cables 40 then extend from the upper spreader 34 to the rear strut 41 pivoted on the rear side of cap 14. Front strut 42 is also pivoted on cap 14 and is connected by fixed length cables 43 to the rear strut 41. Guy line cables 45 of fixed length connect the front strut 42 to the outer end of the jib-boom.

A load line 47 is connected to a load L, is trained over the sheave 48 on the outer end of the boom 15, over the guide sheave 49 on the rear side of the cap 14, and then down and around the power winch drum 8.

Operation When the jib-boom is in the dotted-line position of FIGURE 1, the tower has adequate forward loading. Stated otherwise, the tower leans sufficiently forward or to the right, as viewed in FIGURE 1. When the jib-boom is in the :full-line position shown in FIGURE 1, the forward loading on the tower is negligible. As a result, in the prior art where the lower end of the jib-boom cable drum 9 and anchor are positioned a distance from the tower thereby creating a moment arm through which the load cable can act, the tower actually may lean backward. If the load imposed on the tower is sufiicient, this could capsize the tower over the backstops. The present invention overcomes this serious problem as follows:

With the above jib-boom hoist cable system anchored directly to the tower as on shaft 26, there is no moment arm effective between the tower pivot point 13 and the cable. As a result, when the jib-boom is in the fully elevated position, there is no backward force applied to the tower by the cable 40, as there would be if the anchor point 26 were located a distance spaced from the tower. Even if the load is dropped, or otherwise accelerated, no backward torque is applied to the tower.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention:

1. A mobile tower crane having a crane cab, a vertically disposed tower .pivotally mounted at its lower end to said cab, a tower suspension cable secured to the upper end of said tower and also secured to said cab to prevent forward tipping of the tower, at jib-boom pivotally mounted at one of its ends to the upper end of said vertical tower for vertical swinging movement and for being extended generally vertically above said tower, power hoisting mechanism on said cab, a jib-boom cable reeving means having an anchor point located directly on and adjacent the lower end of said tower whereby there is no effective moment arm between said anchor lPOil'lt and said tower, said reeving means including a cable extending over the upper end of said tower and secured to the free end of said jib-boom, said reeving means being connected to said power hoisting mechanism whereby the latter can operate said reeving means to vertically position said jib-boom.

2. A mobile tower crane having a crane cab, a vertically disposed tower pivotally mounted at its lower end to said cab. a tower suspension cable secured to the upper end of said tower and also secured to said cab to prevent forward tipping of the tower, a jib-boom pivotally mounted at one end to the upper end and front side of said vertical tower for vertical swinging movement and for being extended generally vertically above said tower, a shaft rigidly mounted on the back side of said tower and adjacent the lower end thereof, a jib-boom cable reeving means anchored on said shaft whereby there is no moment arm between said shaft and tower, said reeving means including a cable extending over the upper end of said tower and secured to the free end of said jibboom, and a power winch drum on said tmb, said reevi-ng means being connected with said power drum where-by the latter can operate said reeving means to vertically position said jib-boom.

3. A rubber-tired mobile tower crane having a chassis and a crane cab rotatably mounted thereon, a vertically disposed tower pivotally mounted at its lower end to said cab and having a cap at its upper end, a tower suspension cable secured to the upper end of said tower and also secured to said cab to prevent forward tipping of the lower, a jib-boom pivotally mounted at one end to said cap at one side and the upper end of said vertical tower and having a free end for vertical swinging movement and for being extended generally vertically above said tower, a power hoisting drum on said cab, and a jib-boom multiple-sheave cable reeving means having an anchor point directly on said tower adjacent the lower end thereof whereby there is no moment arm between said reeving means anchor point and said tower, said reeving means including a cable extending over said cap and then secured to said free end of said jib-boom, said reeving means being operatively connected to said power hoisting drum whereby the latter can operate said reeving means to vertically position said jib-boom.

4. A rubber-tired mobile tower crane having a chassis and a crane czrb rotatably mounted thereon, a vertically disposed tower pivotally mounted at its lower end to said cab and having a cap at its upper end, said cap having a front and a rear side, a tower suspension cable secured to the upper end of said tower and also secured to said cab to prevent forward tipping of the tower, a jib-boom pivotally mounted at one end to the front side of said cap, said jib-boom being vertically swingable to a working position generally vertically above said tower, a power hoisting drum on said cab, a shaft rigidly mounted on the back side of said tower and adjacent the lower end thereof, a jib-boom multiple-sheave cable reeving means anchored on said shaft whereby there is no moment arm between said shaft and tower, said reeving means having a cable extending over said cap and secured to said jibboom, said reeving means also having an operating connection with said power hoisting drum whereby the latter can operate said reeving means to vertically position said jib-boom without acting through a moment arm between said reeving means and said shaft on said tower.

References Cited by the Examiner FOREIGN PATENTS 497,449 12/ 1919 France. 1,132,579 11/1956 France. 1,347,727 11/ 1963 France. 1,100,248 2/1961 Germany.

990,678 4/ 1965 Great Britain.

EVON C. BLUNK, Primary Examiner. HUGO O. SCHULZ, Examiner.

A. LEVINE, Assistant Examiner. 

1. A MOBILE TOWER CRANE HAVING A CRANE CAB, A VERTICALLY DISPOSED TOWER PIVOTALLY MOUNTED AT ITS LOWER END TO SAID CAB, A TOWER SUSPENSION CABLE SECURED TO THE UPPER END OF SAID TOWER AND ALSO SECURED TO SAID CAB TO PREVENT FORWARD TIPPING OF THE TOWER, A JIB-BOOM PIVOTALLY MOUNTED AT ONE OF ITS ENDS TO THE UPPER END OF SAID VERTICAL TOWER FOR VERTICAL SWINGING MOVEMENT AND FOR BEING EXTENDED GENERALLY VERTICALLY ABOVE SAID TOWER, POWER HOISTING MECHANISM ON SAID CAB, A JIB-BOOM CABLE RECEIVING MEANS HAVING AN ANCHOR POINT LOCATED DIRECTLY ON AND ADJACENT THE LOWER END OF SAID TOWER WHEREBY THERE IS NO EFFECTIVE MOMENT ARM BETWEEN SAID ANCHOR POINT AND 